As the climate warms, governments, companies and organizations across the world are scrambling to halt greenhouse gas emissions. But massive amounts of carbon dioxide are being emitted every day.
The atmospheric CO2 concentration was 418.51 parts per million (ppm) Tuesday, according to the National Oceanic and Atmospheric Administration. About 350 ppm of CO2 in the atmosphere is what experts agree is a reasonable level. While technology and governmental regulations evolve to reduce emissions, many are looking into carbon capture and storage (CCS) or carbon capture and usage (CCU) to lower their current climate impacts.
“One of the big factors driving CCS growth is recognition that achieving net-zero greenhouse gas emissions is increasingly urgent,” the Global CCS Institute’s 2020 report said. It said CO2 capture and storage capacity was more than 110 million metric tons per year in 2020, which is the amount of CO2 135 million acres of U.S. forests can sequester in one year. About one-third of that CCS capacity was operational, two-thirds was in early or advanced development and a small portion was in the construction phase.
CCS technology often captures CO2 and pumps it underground into porous rocks with nonporous rocks above, trapping the CO2 there indefinitely. Alternatively, CCU technology can use the CO2 for synthetic fuel manufacturing, concrete production, algae growth, plastic production or soft drink carbonation.
CO2 can be captured in one of two ways. The first, direct air capture (DAC), is when carbon is captured directly from ambient air. The second is when CO2 emissions are captured from flue gases as an industrial source emits them.
The case for DAC
Because CO2 is equally distributed in ambient air, DAC facilities can be built virtually anywhere. The freedom of location means that DAC can be installed close to where the captured carbon will be used or pumped underground, dramatically reducing transportation costs. Companies can scale DAC to whatever size and capacity they need, which is often not the case when retrofitting industrial, carbon-emitting plants.
Even if all feasible industrial sources worldwide captured CO2 on-site, companies such as Climeworks and Carbon Engineering could use DAC to continue to lower CO2 concentrations in the atmosphere by capturing carbon from ambient air anywhere.
Capturing CO2 from industrial sources
Capturing carbon from air with higher concentrations of CO2 makes this option much less expensive per ton of CO2. Carbon capture company Carbon Clean aims to capture CO2 for $30 or less per ton, stating it is 30% more commercially viable than competitors.
According to the World Resources Institute (WRI), DAC costs can vary from $250 to $600 per ton of CO2 captured. The WRI said that number is expected to drop to $150 to $200 per ton of CO2 in the next five to 10 years. Even if costs dropped to $150 per ton of CO2, it is still five times higher than the cost of Carbon Clean’s captured CO2 from industrial sources today.
Carbon capture, usage and storage considerations
Using CO2 in products such as fuel or soft drinks only stores carbon briefly, as it is released back into the atmosphere much faster compared to products such as concrete or plastic.
Captured CO2 can be used as a strengthening agent in concrete, which could be in use for decades and has the potential to be recycled and reused without releasing the CO2 into the atmosphere. However, a 2021 Nature study questioned whether using captured CO2 in concrete produces a net climate benefit because of the energy and transportation requirements for CCU.
Permanent storage of CO2 deep underground is often referred to as carbon sequestration. There is some concern about the long-term availability of sequestration options for CO2 since specific rock formations are needed to prevent CO2 leakage.
“CCS is one of the most mature and cost-effective options” for hard-to-abate industries to achieve net-zero emissions, the Global CCS Institute report said.